ULMACEAE 



The Elms 

 Characteristics of the Genus Ulmus L. 



HABIT. Handsome trees often planted for shade or orna- 

 mental purposes; irregularly pinnate branching. 



LEAVES. Alternate; simple; deciduous; lanceolate to obo- 

 vate; stipulate; penniveined; simply or more commonly doubly 

 serrate; 2-ranked; mostly unequal and oblique at the base and 

 acuminate at the apex. 



FLOWERS. Regular; perfect; small; in fasiccles or cymes; 

 appearing before the leaves (in a few species not appearing until 

 autumn) ; on slender, drooping pedicels ; calyx 5-9 lobed ; corolla 

 absent; 4-6 stamens; ovary usually 1 -celled by abortion, 1- 

 ovuled, flattened, with a deeply 2-lobed style. 



FRUIT. An oblong to suborbicular samara; maturing in the 

 spring or autumn of the first year; surrounded at base by rem- 

 nants of calyx; seed cavity compressed and surrounded by a 

 thin papery wing which is commonly notched at the apex and 

 tipped with the remnants of the persistent style. 



TWIGS, Slender to stout; somewhat zigzag; with corky wings 

 on some species; pith solid, round, Winter buds: terminal absent, 

 lateral with overlapping scales, 



BARK. Thick and furrowed; often with layers of 2 colors. 



WOOD. Moderately important; heavy, hard, strong, and 

 tough; ring-porous; not durable; difficult to split; specialized 

 uses. 



SILVICAL CHARACTERS, Rather tolerant trees: fast- 

 growing; wide-spreading, lateral roots. 



GENERAL. This genus contains about 20 species of trees 

 scattered through the Northern Hemisphere; many are among 

 our most important shade and ornamental trees. Six species 

 are native to North America, Five exotic species which are 

 commonly planted in this country are included in the key; of 

 these U. pumila, which is widely grown in the central and western 

 States, has been naturalized from Kansas to Minnesota. 



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